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Topic Title: Help
Topic Summary: Voltage regulator not working
Created On: 02 August 2011 11:38 AM
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 02 August 2011 11:38 AM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

I am testing a volatge regulator before Populating a PCB.
the voltage regulator is a 25Vinout and a fixed output of 12V its an LDo regulator. I have been testing it the point is it is not giving any output even when I added a load of 1K it still does nothing I tried two of the regulators but same result.

This is the manufacture code for the Regulator BAJ2CC0WT,

I will appreciate any help offered.
 02 August 2011 11:57 AM
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ANFierman

Posts: 136
Joined: 25 July 2008

Simply saying "I'm using device X and it doesn't work" will not get you very far.

You need to post your test circuit diagram and PCB/breadboard layout somewhere so people can see them before anyone can give you any sensible advice.

Some notes about how you are testing it and what test equipment you're using would be very helpful too.



-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 02 August 2011 12:20 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

Thanks for that, I have placed my regulator on a breadboard I am using a power supply to inject 25V at the input pin and using a DMM to check if its regulating it down to 12V, on the breadboard i have connected a 1K resistor between output and ground in parallel with a 22uF as suggested in the datasheet. But still I cannot observe any voltage on the output. hope that this explains it more.
this is the datasheet link for the regulator used http://www.farnell.com/datasheets/614207.pdf
 02 August 2011 12:34 PM
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ANFierman

Posts: 136
Joined: 25 July 2008

What have you connected the control pin (1) to?
Ground?
Vin?

BTW: manufacturers data is here:
http://www.rohm.com/products/l...l/regulator/baj2cc0wt/

-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 02 August 2011 01:07 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

connected it to ground as I did not thinks I will need. I thought that the ctrl pin was for adjusting.
 02 August 2011 01:42 PM
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ANFierman

Posts: 136
Joined: 25 July 2008

"I thought that the ctrl pin was for adjusting."

Just demonstrates how you have to be very careful reading the datasheets for devices.

It controls the shut down switch.

That said, the version of the datasheet pointed to by Farnell is useless.

The manufacturers datasheet is not much better but this from p8 of there:

"CTL Terminal
The CTL terminal is turned ON at 2.0V and higher and OFF at 0.8V and lower within the operating power supply voltage range.
The power supply and the CTL terminal may be started up and shut down in any order without problems. "

may explain your problem.

The information is there in the Farnell version of the sheet but implied only by the "Shutdown current" and "Bias current" entries in the electrical characteristic table on p2.



-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 02 August 2011 02:00 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

So if I use 24 Volt for that will it be ok or I have on my board two regulators one is 12V and the other is 5V I am thinking of pwering the ctrl pin from the 5 V will taht be ok.

Thanks for your Help Its much appreciated, Thanks
 02 August 2011 02:37 PM
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ANFierman

Posts: 136
Joined: 25 July 2008

Depends:
i) what sort of regulators the 12V and 24V parts are you using?
ii) do you care about the order in which your rails come up?

If the 12v and 5V regulators are the same type as the 24V then they'll never start because the 5V can't come up until its ctrl pin goes >2V and the ctrl pin can't go > 2V until the 5V rail comes up etc., etc.

If you drive the ctrl pin from the 5V regulator o/p then 24V can't come up until 5V is up.

If you aren't fussy about rail sequencing then just tie the ctrl pin to the input pin.

-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 02 August 2011 03:08 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

The 24 V is comming out of the power supply to supply both the 12V and the 5V regulator. The 5V have an adjusting pin but I do not require anyadjusting as I need it to supply 5v at 2.5A. the datasheet (http://www.farnell.com/datasheets/42567.pdf)

so my idea is to take a link from the output of the five to power the ctrl of the 12V regulator.

thanks
 02 August 2011 03:43 PM
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ANFierman

Posts: 136
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OK. Sorry, misunderstood. In your earlier posts you had talked about having a 24V regulator and I forgot you were now talking about the 24V to 12V regulator.

-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 02 August 2011 03:54 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

yes thats it so can I use the output of the 5V to trigger the control pin
 03 August 2011 09:32 AM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

I have applied a 5V to the ctrl pin of the 12V still no result
 03 August 2011 10:52 AM
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ANFierman

Posts: 136
Joined: 25 July 2008

Have you grounded the ground pin and/or the tab on the 12V reg package?
Have you respected all the notes about decoupling the RoHm reg?
Does it get hot?
Checked with a scope to see if oscillating?
Does the 5V reg work?

Need pictures and cct diagram.

An easy and quick way to do this is to create a website using Google Sites and share it with everyone (make it public) and then post pictures etc. there. Or upload them as files into Google Docs and make them public.

-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 03 August 2011 11:29 AM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

at the moment I am using a power supply to provide the 2 volt to the ctrl. the package is not getting hot the ground pin is grounded and I am using a 22uF between output and ground as they required in the data sheet but still nothing.

the 5V regulator works perfectly and I used it earlier to supply the ctrl of pin1 of the 12V regulator and that also did not work. I even used a different 12V regulator just in case the one I am using is damaged but same result.

I will try to upload pictures on a google doc.
 03 August 2011 02:29 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

Thanks very much for your help Mr Fierman, it is working now.
I appreciate you taking some of your time to help.

Respectfully Yours

Mohamad Hijazi
 03 August 2011 02:35 PM
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ANFierman

Posts: 136
Joined: 25 July 2008

My pleasure ... but do tell: what was the missing bit of magic that made it work?

-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 03 August 2011 03:37 PM
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MHIJAZI84

Posts: 56
Joined: 25 July 2008

Hello

the first problem was the ctrl, i should have applied a 2V or above for that. but after that it was some equipment setting that I was using for the measurement. Did not see that one coming.
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